The invention relates to a protection device for the railroad industry. In particular, the protection device is designed to limit the likelihood of train incursions into a forbidden zone, or beyond a certain boundary, which may contain a hazard such as another train, an open switch, an open lift bridge or a work crew, among others.
The movement of trains on railroad tracks is usually controlled by a signaling system that is analogous to the traffic lights used on public streets and highways. One problem with this approach is that compliance with the signal being directed to a particular train is dependent upon the attention of the train operator. If the operator is inattentive, distracted or even unconscious, a signal that requires that the train be stopped may go unnoticed, and this might create a potentially hazardous situation.
Against this background, it clearly appears that there is a need in the industry to provide a protection device that functions automatically in a way to reduce the likelihood of train incursions into a forbidden area or beyond a certain boundary.
Under the first broad aspect, the invention provides a protection device that is designed to be used in conjunction with a remote-controlled braking system of a train. Such a remote-controlled braking system includes a first functional unit that is mounted in the locomotive of the train and a second functional unit mounted in a car that is either pushed or pulled by the locomotive. The first and the second functional units are connected to one another by a radio frequency (RF) link. Such RF link allows the first functional unit to transmit to the second functional unit a brake command such that the second functional unit can apply the brake of the train. Such remote-controlled braking systems are designed as emergency devices allowing the brake of the train to be applied at a location other than the locomotive if for some reason a brake malfunction develops.
The protection device includes a transmitter that is operative to transmit an RF signal for introduction in the RF link to cause the second functional unit to apply the brake of the train in response to the reception of a brake command by this same second functional unit. Such an application of the brake will cause the train to stop or decelerate. The expression xe2x80x9capply the brakexe2x80x9d in the context of this specification means that either braking action of the train is initiated or, in the case that the braking action is already initiated, that braking action is augmented.
Under a specific example of implementation, the protection device is a wayside installation and receives an input from a detector that detects the position of the train relative to a certain boundary that the train is not authorized to cross. For example, the detector can be a proximity detector that is triggered when the train passes close to the detector. Such a proximity detector can be of the type that uses a light beam that is broken when the train passes through the beam. Other possibilities include magnetic detectors, pressure sensors and a wide variety of other devices that can issue a signal when a train passes within a certain detection range.
In conventional railway systems, the detector that detects the position of the train is implemented by an electrical circuit formed of the track rails, a source of signal voltage, a relay energized by the signal voltage and the train itself. The presence of the train shunts the signal voltage, thus releasing the relay and thereby detecting the presence of the train in an allowed track area or its incursion into a forbidden area. Another conventional detector implements wheel counter logic for counting the wheels of the train as it passes by, thus determining when the train has vacated a particular track segment and entered the next one. In another example, the detector is a transponder (a low frequency or radio frequency transmitter and receiver) which replies to a signal from the train when it passes over, by indicating a number or code identifying the position as if it were a signpost.
The protection device can be installed immediately adjacent to the traffic signal. When the traffic signal is enabled to indicate to the train operator that the train should stop, the protection device is also enabled. If the train enters within the detection range of the detector, which indicates that the operator of the train has not seen the signal or is unconscious and cannot obey the signal, the transmitter issues a brake command which is received by the second functional unit and interpreted by the second functional unit in the same way as if this brake command was generated by the first functional unit.
The advantage under this approach is that the protection device can be deployed without any modification to the trains. This is a significant practical advantage over other devices that require installation of components on the trains.
The format of the brake command issued by the transmitter can vary and usually will depend on the particular data communication protocol established for the RF link. In one possible example, the RF link is used to exchange signals having different frequencies, the frequency of the signal conveying information to be transmitted between the two functional units. Under this approach, the brake command is a signal at a specific frequency that indicates to the second functional unit to apply the brakes. Under a different possibility, the signals transferred over the RF link are digital signals. In particular, those signals are coded, each code being represented by a different combination of bits. The introduction of a brake command in the RF link is effected by sending a signal from the transmitter of the protection device which includes the particular combination of bits that would be interpreted by the second functional unit as a command to apply the brakes. Under a more sophisticated communication protocol, the protection device may need to first intercept a communication between the two functional units in order to extract data elements that are necessary to construct the brake command. In particular, such communication protocol may be based on the exchange of data packets, each data packet including the address of the first functional unit (uniquely identifying the sender of the data packet) and the address of the second functional unit (uniquely identifying the receiver of the data packet). Such addressing scheme is used to prevent reception and execution of commands by an entity other than the entity to which the command was originally destined. In particular, when two or more trains operate in close proximity to one another, this addressing scheme avoids situations where the command issued by the first functional unit of one train is received and executed by the second functional unit of another train.
Objectively, when the RF link conveys data packets with an addressing scheme, the protection device needs to receive a data packet such as to extract the address information before constructing the brake command. This may require a modification of the first and second functional units such that an exchange of data packets is effected either continuously or through a triggering mechanism when the train approaches the protection device.
Under a possible variant, the protection device is designed to send a signal in the RF link that is not a direct brake command, rather it is designed to trigger the generation of a brake command by the first functional unit. For instance, the signal issued by the transmitter may stimulate an emergency signal that may be issued from the second functional unit and that is designed, under normal circumstances, to cause the first functional unit to issue a brake command. Thus, the brake command is implemented by the second functional unit or, alternatively, the brake command is implemented by the first functional unit.
Under another variant, the protection device is mounted on the train. The detection of the train position with respect to the unauthorized zone or boundary can be done by a GPS based device.
Under a second broad aspect, the invention provides a protection device for use with the remote-controlled braking system of the train having a locomotive and at least one car, the remote-controlled braking system including a first functional unit for mounting in the locomotive of the train and a second functional unit for mounting in the car. The first functional unit and the second functional unit are operative to establish an RF communication link between them. The first functional unit is operative to transmit to the second functional unit a brake command over the RF communication link to cause the second functional unit to apply the brake of the train. The protection device includes the detector for generating a detector signal when a certain condition occurs. In addition, the detector includes a transmitter to transmit an RF signal for introduction in the RF communication link to cause the second functional unit to apply the brake of the train in response to the reception of a brake command by the second functional unit.